Method for the separation of oil and water from an emulsion

ABSTRACT

Facilitating and expediting separation of oil/water emulsions by passing the emulsion as a surface film on a rotating pick-up roller into a bight formed by a closely spaced parallel rollers to coalesce the oil particles, break the emulsion and liberate free oil.

[151 3,685,653 51 Aug. 22, 1972 United States Patent Van Stavern et al.

m Mm C mm m 5/1921 Foster....................210/402X 5/1932 Schamberger.........210/402X Van Stavern; Henry D. Moorer; Gordon H. Miller; Kenneth M. Gunn, all of Richmond, Va.

[73] Assignee: Texaco, Inc., New York, NY.

June 25, 1971 Primary Examiner-J; L. DeCesare [22] Filed:

Azt0rney--Thomas l-l. Whaley et al.

21 Appl. No.: 156,643

Related US. Application Data [63] Continuation-impart of Ser.

Nos. 46,056, June 1970, abandoned, and 46,057, Facilitating and expediting separation of oil/water Ju 1970, 3,612,277- emulsions by passing the emulsion as a surface film on a rotating pick-up roller into a bight formed a 210/242 closely spaced parallel rollers to coalesce the oil partin cles, b eak th d H) t f 1 58 Field 0fSearch.........2lO/77, 402, DIG. 21, 242, r e e era 6 me o .2 m B e Figures a vmmcmuczz m2 3.685653 SHEET 2 BF 4 FIG. 2

PKTENTED M1822 m2 SHEET b 0F 4 -E E5 m om IODOQTC. cwmmda J mwksz GAP SETTING (mils) METHOD FOR THE SEPARATION OF OIL AND WATER FROM AN EMULSION This application is a continuation-in-part of US. Pat. application Ser. No. 46,056 filed June 15, 1970, now abandoned, which in turn was copending with patent application, Ser. No. 46,057 filed June 15, 1970 in the name of Merle H. Van Stavem, Wylie T. Jones and Howard F. Cossay, now US. Pat. No. 3,612,277, patented Oct. 12, 1971, concerns a method and apparatus for recovering oil slicks from marine surfaces at a reasonable rate of recovery with a limited pick-up of water with the oil.

The present invention relates to the separation of oil and water, and more particularly to the breaking of oil/water emulsions.

It has been the practice to separate various emulsions, if possible, by settling, centrifuging and the like or by the use of chemical means.

In general, however, even without problem emulsions, a significant period of time is required for separation. This is advantageous in connection with the disposal of the recovered oil by, for example, conducting it to a receiving tank, inasmuch as the oil capacity of the receiver is limited by the water. Therefore restriction of the water picked up with the oil makes possible more efficient use of the equipment.

Stated in another way, when oil is recovered by a roller which dips down into the layer of oil and carries it up to a doctor blade, the oil tends to be accompanied by a film of water. At higher rates of roller rotation and recovery there is usually greater water contamination. For this and other reasons apparent from the aforesaid application it may be beneficial to decrease the quantity of water which is recovered with the oil.

In accordance with the present invention we have discovered that the foregoing method and equipment used in the recovery and clean up of oil spills, appropriately adjusted, operates to break emulsions of oil and water.

Such emulsions are found in a vast number of industrial operations; for example, field emulsions from producing wells, or emulsions in circulating lubricating oil systems such as the oil system of a turbine or steam engine.

The present invention therefore contemplates means and steps for accelerating the breaking of an emulsion, an objective which is of particular significance with todays demand for clarification of increased quantities of water. This is accomplished by picking up on the surface of a rotating roll, a coating of emulsion which is then brought into contact with a supplemental or socalled transfer roll located above and out of contact with the body of emulsion. The transfer roll is spaced closely from the first named roll or pick up roll a critical distance in the range of 1 to 6 mils effective to cause the minute particles of dispersed oil to coalesce and segregate.

In order to illustrate a preferred form of our invention reference is made to the figures of the attached drawing wherein FIG. 1 is a perspective view of a fragmentary portion of a pick-up float or vessel constructed in accordance with the present invention;

FIG. 2 is an elevation taken from the rear of the device of FIG. 1 with portions of the recovery trough and baffle broken away to show the underlying structure;

FIG. 3 is a sectional view taken on the line 33 of FIG. 2, and

FIG. 4 is a detailed fragmentary view of an adjustable journal for the transfer roller;

FIG. 5 is a typical performance carve showing the operations of the present system.

Referring now to the figures in the drawing, 10 represents the frame of the device which is carried by a pair of floats 12 which may take the form of any suitable marine vessel. Where it is desired to arrange the oil pick-up device over a fixed channel, the frame can be simply mounted on fixed supports over the channel.

A pick-up roller, comprising cylinder 14, is joumaled as at 16 in frame 10. Roll 14 is so arranged that its lower extremity dips into the water surface 18 as at 20.

A supplemental or transfer roller comprises cylinder 22, likewise joumaled at 24 on the frame 10 and located in a position substantially above and out of contact with the oil slick 38.

Pick-up troughs 26 and 28 are arranged respectively adjacent the pick-up roll 14 and transfer roll 22 -to receive film removed byscrapers or doctor blades 30 and 32, which bear against the respective rollers. The rollers may be rotated in opposite rotational directions by drive motor 34 and suitable belt and gear drive 36, as shown more clearly in FIG. 2 so that the rollers move, at their point of close juxtaposition, at approximately the same speed and the same direction.

As indicated more clearly in the more or less diagrammatic FIG. 3, the roller 14 rotates in a counter clockwise direction. This is a good arrangement where the direction of movement of the vessel is toward the left as viewed in the figure or where a flow of oil is from the left. In this arrangement the rotating surface which has just passed the doctor blade first contacts oil layer 38 and carries the adherent oil downwardly and (if the oil layer is thin) through the water surface. Thereafter it emerges and proceeds up to the bight between rolls l4 and 22, at which point the surface of roll 22, rotating in the opposite angular direction, contacts the oil layer as shown.

Means are provided as shown more clearly in FIGS. 3 and 4 for adjusting the spacing between the parallel rollers 22 and 14, comprising a projecting journal support 40 welded to the frame 10 as at 42 and provided with a central recess 43 to accommodate shaft 44 and journal 46 of roller 22.

The shaft 44 of roller 22 and the journal 46 ride in an adjust box or sleeve 48 which is supported by the journal support 40. Adjustment of the box 48 inwardly or outwardly along support 40 causes roller 22 to move transversely toward or away from the pick-up roller 14 to adjust the spacing therebetween.

This adjustment is accomplished by machine bolt 50 which is threaded thru the box 48 and contacts the journal support 40 as at 52.

The roller spacing or gap is appropriately adjusted until the liquid squeezed out between the bight of the two rollers, as well as that recovered in the respective troughs 26 and 28 shows maximum separation of the emulsion.

In operation, roller 14 dips into an oil-water emulsion as indicated in FIG. 3, carrying a film thereof up into the bight between rollers 14 and 20.

It usually happens that oil emulsions are associated with separate streams of oil or water as, for example, a

stream of oil-water emulsion floating on a stream of vapor-oilrwater emulsion floating of water or/on a layer of oil, floating, in turn, on the water. In any event it is desirable to rotate the pick-up roll down into the emulsion layer and, if necessary, therebelow so as to continuously conduct a film of oil thru the rotational paths up into the bight between the rolls.

In general, emulsion breaking follows, as above indicated, a close setting of the two rolls, in the range of about 1-6 mils. The emulsion being conveyed into the bight between the two rolls is subjected to a squeeze or compression action. It has also been found that the total amount of liquid which is picked up by the transfer roll 22 decreases as the roll spacing is increased above about 2-3 mils. Therefore, it is advantageous to merge the two rolls and preferably considerably smaller than this, as for example, a spacing of l-4 mils.

By way of exemplifying the present invention a series of tests were run using a laboratory scale piece of roller pick-up and transfer device identical in arrangement with that shown in the attached drawings, but modified to provide a relatively small trough, closely fitted under the pick-up or main roll so that the emulsion is continuously fed into contact with the roller until essentially all of the feed stream has been picked up.

One emulsion employed for the present tests comprises a 2 percent water emulsified in a continuous phase of Code 1562 Capella oil, wax free Grade D having the following properties:

Appearance Pale Yellow Blue Bloom Gravity 25.3

Flash, COC 400 Fir, COC 445 Color. ASTM Ll.5

Pour, F. 35

Vis, SUS at 100F. 313

Vl(D-2270) 18 Freon Haze 55 Freon Flock 70 The separation properties of the emulsion during quiescent holding show about 72 percent of the water settled out of the emulsion at 90 hours of standing time.

The data derived from the operation of the dual roller pick-up and transfer device were as follows, using rollers having a teflon surface rotated at 80 rpm in each instance:

Water Cll6Cld (CC )Accumw percent Roll No. Charge Product lated of Water Spacing Cycles Trough Pan Total Removed 2 mil. 1 8.0 5.0 13.0 66.6 [-1.5 mil l 13.5 2.1 15.6 80.0 2 1.2 0.2 l7.0 87.3

In other words, it is to be noted that the demulsification figures above represent not only product (both oil and water) recovery in troughs 26 and 28 but also the product which has been returned to the charge trough.

This has many beneficial possibilities. First, the troughs 26 and 28 may be omitted so that the entire product is continuously returned to the original reservoir. This may be particularly advantageous and economical in treating the contents of a large settlement basin or reservoir where the separated oil and water proceed to stratify below the upper layer of emulsion. In other words, the present equipment, arranged in a settling pond of this type, does not require any alteration of the system but simply accelerates the separation.

As a result, the treatment capacity of the pond is correspondingly increased.

While the applicants do not wish to be bound thereby, they nevertheless speculate that the constricting effect of drawing the emulsion into the narrow bight between the rollers tends to coalesce the particles of the dispersed phase into larger and more continuous masses, which, therefore, readily separate out.

Also indicated by the foregoing data is the fact that repetition of the treatment tends to result in yet further emulsion breaking. By way of explanation, reference in thedata to No. Cycles concerns the number of times the treatment was conducted and the numeral 2 in this column in the third row of figures in the table signifies repetition or retreatment of the emulsion which remained unseparated after the previous treatment. This indicates that repeated treatment of the emulsion by the rollers effects yet further separation. This leads to the observation that continuous treatment of the emulsion in an open pond will ultimately efiect a significant improvement in separation.

By way of further example, reference is made to a typical hard emulsion encountered in the product from the barometric condenser of vacuum pipe still in a typical petroleum refinery. Such units operate to effect a distillation of the oil under a vacuum, maintained by injection of steam into a barometric condenser. Some of the oil, carried over from the vacuum still into the con- 5 denser, becomes emulsified with the condensate.

0 slow process of settlement, and the products also include a hard emulsion which does not separate and therefore requires the return of water back into the still, which yet further impairs operation thereof.

The tests were conducted on bench model, dual roller, pick up and transfer device shown in the previous figures with one exception, namely the omission of the doctor blade and pick-up trough on the main pickup roll 14. This arrangement was selected to obviate variables caused by multiple recovery and to enable more consistent test operations.

In the experiments, roll speed was constant at 60 rpm. The roll surface was stainless steel.

Referring to the FIG. 5, the vertical scale shows liquid material passing through the bight between the two rollers thereafter caught and recovered by the doctor blade 32 and pick-up trough 28 on the transfer roll 32expressed milliliters per minute. The curve 5 6 identified by numeral 60 represents the total liquid s breaking of an emulsion of oil and water into indepenrecovered. While 62 represents the recovery of free oil. dent oil and water phases which comprises,

The horizontal scale represents the roll spacing in forming a film of oil/water emulsion on the surface of mils, namely thousands of an inch. a rotating pick-up roll,

The results therefore show a striking and unobvious bringing said film of oil/water emulsion on said picl breaking of a hard, resistant emulsion, which surprisp rol in contact wi h a second roll arrange ll'l ingly reaches a maximum at the rang b tw e 1 d 6 coaxial parallelism to the first roll with its adjacent mils. surface rotating in approximately the same A further phenomenon which seems not to have injection and the same Speed as h h been previously observed is the fact that the transfer of 10 adjacent of the rollers being l p liquid to the transfer roll at first increases with roll Spaced relatlonshlp anfnher a range Spacing and then decreases. of from about 1 to 6 mils at which the minute parti- Surprisingly, moreover, there is greater transfer at an C165 of of the m i coalesce together and intermediate roll spacing of 2-3 mils than when the segregate free Space between the t n is wider l5 2 The method as called for in claim 1 wherein said w claim; roller spacing is within a range from about 1 to 4.mils.

l. The method of facilitating the separation and inIAln nAcq 

2. The method as called for in claim 1 wherein said roller spacing is within a range from about 1 to 4 mils. 